Chilean President Sebastien Pinera described as "insufficient" the agreements reached on Sunday after marathon talks, but said it was not for the host's lack of trying and criticism of its role was unfair.

"You have to convince 195 countries, and so if just one opposes, there is no agreement," Pinera said in comments to local media.

When it came to rules governing carbon markets, he said "the four big countries didn't accept the proposals".

But diplomats have listed Australia, Brazil, China, Japan, Saudi Arabia and the United States among those resisting bolder action.

Pinera said he personally lobbied other presidents to reach a deal, but would not identify who he called and did not name the countries which he said blocked the deal.

"The countries that pollute the most did not live up to the challenge and remain in debt," he said in a subsequent tweet.

Chile had stepped in to preside over the talks after Brazil pulled out following the election victory of right-wing President Jair Bolsonaro. It was then forced to host them more than 10,000 km away in Spain due to unrest at home.

Environment Minister Carolina Schmidt, president of the UN summit known as COP25, came under fire on Saturday for circulating a draft text that campaigners said threatened to undermine the landmark 2015 Paris agreement on carbon reduction.

"If this text is accepted, the low ambition coalition will have won the day," David Waskow of the World Resources Institute, said at the time.

Greenpeace International said the Chileans were being "irresponsibly weak".

Pinera said it was not fair to blame her.

"She did all that was humanly possible," he said.

By extending the talks, Schmidt salvaged a face-saving compromise text during late-night discussions.

It cited the "urgent need" to close the gap between existing emissions pledges and the temperature goals of the Paris agreement to avert catastrophic global warming.

Schmidt said she was "sad and pained" at how nations had failed to find consensus but that the issue of carbon markets - a key sticking point - had tied down the last four summits.

"Neither the will nor the political maturity yet exists from some of the big emitting countries to be able to reach agreement on this," she told a news conference.

Laurence Tubiana, Chief Executive Officer of European Climate Foundation, said to win commitments more in line with the warnings of climate science the next host would need to build broad alliances and force those blocking progress to explain themselves openly.

"It means deploying an intensive diplomatic effort right now," she said.

Britain will preside over the next summit, which will be held in Glasgow in November 2020.

Challenges include Brazil's insistence on a carbon accounting approach others say is baffling and Australia's insistence on carrying over old credits to meet its Paris emissions targets, which others see as an accounting trick.

Australian Associated Press